The present invention relates to multifunctional additives and methods for preparing and using the same. Specifically, multifunctional additives are produced by irradiating and subsequently fragmenting, or micronizing, plant materials, such as raw cotton. A multifunctional additive made in accordance with the method of the present invention has the following attributes: (1) anti-misting properties, (2) low coefficient of friction, (3) is suitable for use as a substitute for talc, as for example in cosmetics and other personal care products, and (4) is suitable as a substitute for asbestos in coating applications.
Radiation processing for modification and enhancement of polymeric material properties has been well documented in the prior art. In particular, electron beam processing has been used to improve thermal, chemical, barrier, impact, wear, and other properties of many inexpensive materials extending their utility to demanding applications typically dominated by higher cost materials. Electron beam processing may result in cross-linking, degradation, or a combination of the two, depending on the nature of the polymeric materials and the dosage of radiation applied. Results of electron beam processing of cross-linkable plastics has yielded materials with improved dimensional stability, reduced stress cracking, higher service temperatures, reduced solvent and water permeability. More specifically, radiation induced cross-linking in polyethylene has resulted in increased modulus, tensile and impact strength, hardness, deflection and service temperature stress/crack resistance, abrasion resistance, creep and fatigue resistance. In contrast, radiation processing can also induce degradative, or scissioning, effects in polymeric materials such as polytetrafluoroethylene (PTFE). Scrap or off-spec PTFE, degraded by electron beam processing, has been identified as useful in the production of abrasion-reducing additives.
PTFE has found a use as a friction-reducing additive in many areas, including the printing ink industry. PTFE additives provide ink formulations with anti-rub properties so that the inks are resistant to smearing and marring. However, PTFE cost is relatively high in comparison to other anti-abrasion additives and therefore PTFE use is often cost prohibitive.
Radiation processing has also been used in degrading high molecular weight cellulose ethers common polymeric materials into low molecular weight cellulose ethers producing low molecular weight cellulose ethers for varying uses. For example, U.S. Pat. No. 5,928,709 to Doenges et al. discloses a method of producing low molecular weight cellulose ethers by irradiation of a mixture of higher molecular weight cellulose ethers and an Arrhenius and/or Bronsted base. The resulting low molecular weight cellulose ethers are suitable as water-binding agents, thickeners and emulsion stabilizes.
Clays and talcs have also found traditional use in the reduction of friction. For instance, clays are currently used in down hole drilling fluids useful in reducing friction during drilling operations. Debris present in a down hole is cleared by pumping clay into the bore hole where the clay lowers the viscosity of the debris and aids in moving the clay to an exit. Ideally, the clay maintains the debris in a suspended mixture without building viscosity. In practice, a significant buildup in viscosity is experienced in this process and the efficiency of clearing debris from down holes using clay is significantly less than desired. The cost of suitable clays may also be prohibitive.
Talc has found wide use as a friction-reducer in personal care products, most notably mascaras and body powders. Although hypoallergenic in nature and therefore safe for contact with the human body, talc suitable for personal care products is expensive to manufacture.
The above-described background highlights the need for multifunctional additives with improved low COF characteristics obtainable at a reduced cost. Such additives should not only be economical to manufacture, but also derived from a cheap but plentiful raw material source. The method of manufacture should also be flexible to accommodate production of additives suitable for a variety of applications.
The invention relates to a method for preparing a multifunctional additive from a raw plant material and, in particular, cotton. The raw plant material is irradiated with an electron beam source to form an irradiated product. During the irradiation, the raw plant material is continually blended to provide a uniform radiation dosage to the raw plant material. Following irradiation, the irradiated product is fragmented, or micronized, to form the additive having an average diameter size less than that of the original raw plant material starting product.
In the preferred embodiment of the invention, the method utilizes raw cotton as the raw plant material.
Prior to the irradiating step of the invention, a granulating step may be included wherein the raw plant material is granulated to reduce the diameter size of the raw plant material before irradiating. In one approach to the invention, the granulating step may reduce the raw plant material to about a xe2x85x9 inch to about a xc2xc inch diameter size prior to the irradiating step.
The irradiation step of the invention utilizes an electron beam source for delivering accelerated electrons to the raw plant material. A suitable dosage may be between about 30 megaRads to about 100 megaRads depending upon the particular application the resulting additive will be used in. A dosage of about 80 megaRads to about 100 megaRads is preferable where the additive will be used in friction-reducing applications. However, the total dosage is preferably administered in multiple low dosage passes.
The micronizing step of the invention is meant to reduce the size of the irradiated product and may be carried out with a jet classifying mill. The micronizing step is intended to reduce the average diameter size of the irradiated plant material to an average diameter size of about 3 microns to 4 microns with 99% of the average diameter sizes being below 10 microns.
In addition to a preparatory method, the invention is also directed to an additive, useful in reducing friction, providing anti-misting properties, and suitable as a substitute for talc and asbestos, produced from a raw plant material having been subjected to irradiation by an electron beam. During irradiation, the raw plant material is continually blended so that the raw plant material receives a uniform dosage of irradiation. The irradiated product is subsequently micronized to form an additive with a reduced diameter. The raw plant material used to product the additive is preferably raw cotton.
An additive according to the invention as described above is useful in reducing the coefficient of friction of a substance and may be mixed with the substance in a sufficient amount to effectively reduce the coefficient of friction of the substance/additive mixture. The substance may be a lubricant/grease, cosmetic formulation, or matting agent.